I just tried to open a rar file using ark and i recieved this error message.
“Pre-released Updates (hardy-proposed)”. The testing area for updates. This repository is recommended only to those interested in helping to test updates and provide feedback.
It’s not open source so it doesn’t fit in with the rest of openSUSE, that’s probably why.
Although I’m not sure under which license the unpack part falls, the compressing part is at least proprietary